subrouting with mux leads to 404

Question

i am trying to create subroutes for my app with gorilla mux

this is my router package:

type IRouter interface {
    Get(uri string, f func(w http.ResponseWriter, r *http.Request))
    Post(uri string, f func(w http.ResponseWriter, r *http.Request))
    Put(uri string, f func(w http.ResponseWriter, r *http.Request))
    Delete(uri string, f func(w http.ResponseWriter, r *http.Request))
    AddPrefix(prefix string) IRouter
    Serve(port string)
}

type MuxRouter struct {
    Router *mux.Router
}

func New(apiVersion string) IRouter {
    constructedRouter := mux.NewRouter().PathPrefix(fmt.Sprintf("/%s/api", apiVersion)).Subrouter()
    return &MuxRouter{Router: constructedRouter}
}

func (r *MuxRouter) AddPrefix(prefix string) IRouter {
    subRouter := r.Router.PathPrefix(prefix).Subrouter()
    return &MuxRouter{Router: subRouter}
}

func (router *MuxRouter) Get(uri string, f func(w http.ResponseWriter, r *http.Request)) {
    router.Router.HandleFunc(uri, f).Methods("GET")
}

and in the main:

appRouter := router.New("v1")
router.RegisterPermissionRoutes(&appRouter, &permissionService)

and finally the function:

func RegisterPermissionRoutes(r *IRouter, s *services.IPermissionService) {
    subRouter := (*r).AddPrefix("/permissions")

    fmt.Println(r)
    subRouter.Post("/", (*s).Create)
    subRouter.Get("/", (*s).FindAll)
    subRouter.Get("/{id}", (*s).FindById)
    subRouter.Delete("/{id}", (*s).Delete)
    subRouter.Put("/", (*s).Update)
}

but the problem is that there is no route with "permission" endpoit i don't know what am i missing